1. Field of the Invention
The present invention relates to a printhead and a printing apparatus and, more particularly, to printhead that performs printing in accordance with, for example, an inkjet method and a printing apparatus that performs printing using the same.
2. Description of the Related Art
The element substrate of a printhead included in an inkjet printing apparatus (to be referred to as a printing apparatus hereinafter) is formed from a semiconductor integrated circuit. The ink discharge amount is known to increase as the temperature of the element substrate rises. On the other hand, a printing apparatus is required to guarantee reproducibility and color stability of printed images even in continuous printing. There has conventionally been proposed a technique of precisely controlling the driving voltage or driving pulse of a printhead (see Japanese Patent Laid-Open No. 2007-069575). With this technique, a signal processing circuit of a printing apparatus coordinates the driving condition (driving voltage or driving pulse) of printing elements based on temperature data detected by a temperature detection element integrated on an element substrate and controls to uniform the ink discharge amount.
To implement printing at a higher speed, there has been proposed a technique of increasing the print width of a printhead by arranging a plurality of element substrates in the arrayed direction of printing elements. An example of this proposal is a full-line printhead having a print width equal to or more than the width of a print medium in advance. A full-line printhead enables high-speed printing because its printhead need not be scanned, and is finding increased use in printing apparatuses for business or industrial application purposes. A technique of including a temperature detection element on each element substrate of the full-line printhead and individually detecting the temperature of each element substrate has been proposed (see Japanese Patent Laid-Open No. 2012-121184).
A plurality of element substrates are included on the printhead. For this reason, when a temperature detection element is provided on each element substrate, wires for the temperature detection elements are necessary as many as the number of element substrates, and the number of terminals and the number of wires provided on the head largely increase. This leads to a bulky printed board and an increase in the number of connectors, and consequently to an increase in cost.
When a diode is used as the temperature detection element, a small voltage change caused by the temperature characteristic (−2 mV/C°) of the forward voltage of a PN junction needs to be detected. On the element substrate, however, digital signal lines configured to transfer a data signal, a clock signal, and the like are arranged adjacent to the temperature detection signal line. Noise from the digital signals is superimposed on the temperature detection signal, resulting in an error in the detected temperature. In particular, since the full-line printhead has a large width, the temperature detection signal line to each element substrate needs to be led a long distance. Hence, the temperature detection signal line is readily affected by other signal lines, and noise is readily superimposed.